The pattern of repeating properties of elements revealed in the periodic table is known as the periodic law

… the properties of elements repeat periodically as the atomic number increases.

Explanation:

When you arrange the elements according to their atomic numbers, you find that similar properties recur periodically.

For example, atoms with numbers 3, 11, 19, 37, 55, and 87 are all soft metals that react readily with water.

Elements 4, 12, 20, 38, 56, and 58 are harder metals that react less readily with water , etc.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

c) should be the answer.